Magnetic resonant methods which utilize interaction between magnetic field and nuclear spins in order to form two-dimensional or three-dimensional images are widely used nowadays, notably in the field of medical diagnostics.
Usually, magnetic devices comprise a superconducting main magnet for the generation of static B0-field in an examination zone, gradient coils for the generation of switched magnetic field gradients during the imaging sequence, and a radio frequency (RF) coil assembly. The RF coil assembly of known magnetic resonant devices includes a transmit coil to generate B1-field for excitation of nuclear spins, and one or more receiving antennas used in conjunction with the transmit coil to detect and receive the magnetic resonant signals. Typically, the receiving antennas of the RF coil assembly are connected to a remote receiver system via a bundle of coaxial cables and wires with bazooka baluns. Additionally, the receiving antennas of the RF coil assembly are supplied power via a series of DC cables.
It is believed that the cabling between magnetic resonant receiving antennas and the remote receiver system can be replaced by wireless transmission of the received magnetic resonant signals. Furthermore, a rechargeable battery or a capacitor can be incorporated in magnetic resonant devices in place of the DC cables. In order to keep the battery/capacitor charged, the RF energy generated by the transmit coils can be picked up by a pick-up coil operating at the same resonant frequency as the magnetic resonant signals. The RF energy is further rectified to provide the necessary power for battery/capacitor charging. Such wireless power scheme will result in B1-field inhomogeneity due to pick-up coil interference. As a consequence of B1-field inhomogeneity, the image quality will degrade.
Another wireless power scheme is found in the journal article “Power scavenging circuit for wireless DC power” by M. J. Riffe et al., proceedings of the international society for magnetic resonance in medicine, ISMRM, 5 May 2007, page 3273. In this wireless power scheme, RF power that would normally be dissipated in a detuning network is captured by inductively coupling to the receiver coil's detuning circuit a power scavenging circuit. However, the receiver coil is facing the risk of improper detuning. US 2012/313645 A1 by Biber Stephan et al. provides an energy receiving antenna for inductively receiving energy from an temporally varying magnetic field. US 2014/218035 A1 by Okamoto Kazuya discloses a power transmitting unit wirelessly transmits electric power to an RF coil device by magnetically coupled resonant type wireless power transfer. However, these wireless power transfer means will increase system complexity and cost.